Preparation and properties of hydroxide conducting membrane of poly(tetra phenyl ether sulfone) containing pendant quaternary ammonium hydroxide group for alkaline fuel cell application

Poly(tetra phenyl ether sulfone)s (PTPES) were functionalized with quaternary ammonium salt groups in order to investigate their properties as novel polymeric hydroxide exchange membrane materials. The PTPES-QAH (quaternary ammonium hydroxide)s were synthesized via chloromethylation of PTPESs, followed by reactions with chloromethylmethylether and ZnCl₂, SOCl₂ as Lewis acid catalyst, and then quaternized ammonium hydroxide with immersion of trimethylamine solution. The presence of CH₂Cl groups in chloromethylated PTPES and PTPES-QAH were confirmed by ¹H-NMR. Different contents of ammonium unit of PTPES-QAH (15, 20, 25 mol% of BHPTPB) were studied by FT-IR, ¹H NMR spectroscopy, and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of PTPES-QAH with water. The ion exchange capacity (IEC) and proton conductivity of PTPES-QAH were evaluated with different degree of quaternization.